initial commit, 4.5 stable

core/os/safe_binary_mutex.h

@@ -0,0 +1,145 @@
+/**************************************************************************/
+/*  safe_binary_mutex.h                                                   */
+/**************************************************************************/
+/*                         This file is part of:                          */
+/*                             GODOT ENGINE                               */
+/*                        https://godotengine.org                         */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
+/*                                                                        */
+/* Permission is hereby granted, free of charge, to any person obtaining  */
+/* a copy of this software and associated documentation files (the        */
+/* "Software"), to deal in the Software without restriction, including    */
+/* without limitation the rights to use, copy, modify, merge, publish,    */
+/* distribute, sublicense, and/or sell copies of the Software, and to     */
+/* permit persons to whom the Software is furnished to do so, subject to  */
+/* the following conditions:                                              */
+/*                                                                        */
+/* The above copyright notice and this permission notice shall be         */
+/* included in all copies or substantial portions of the Software.        */
+/*                                                                        */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF     */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY   */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,   */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE      */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
+/**************************************************************************/
+
+#pragma once
+
+#include "core/error/error_macros.h"
+#include "core/os/mutex.h"
+#include "core/typedefs.h"
+
+#ifdef THREADS_ENABLED
+
+GODOT_CLANG_WARNING_PUSH_AND_IGNORE("-Wundefined-var-template")
+
+// A very special kind of mutex, used in scenarios where these
+// requirements hold at the same time:
+// - Must be used with a condition variable (only binary mutexes are suitable).
+// - Must have recursive semnantics (or simulate, as this one does).
+// The implementation keeps the lock count in TS. Therefore, only
+// one object of each version of the template can exists; hence the Tag argument.
+// Tags must be unique across the Godot codebase.
+// Also, don't forget to declare the thread_local variable on each use.
+template <int Tag>
+class SafeBinaryMutex {
+	friend class MutexLock<SafeBinaryMutex<Tag>>;
+
+	using StdMutexType = THREADING_NAMESPACE::mutex;
+
+	mutable THREADING_NAMESPACE::mutex mutex;
+
+	struct TLSData {
+		mutable THREADING_NAMESPACE::unique_lock<THREADING_NAMESPACE::mutex> lock;
+		uint32_t count = 0;
+
+		TLSData(SafeBinaryMutex<Tag> &p_mutex) :
+				lock(p_mutex.mutex, THREADING_NAMESPACE::defer_lock) {}
+	};
+	static thread_local TLSData tls_data;
+
+public:
+	_ALWAYS_INLINE_ void lock() const {
+		if (++tls_data.count == 1) {
+			tls_data.lock.lock();
+		}
+	}
+
+	_ALWAYS_INLINE_ void unlock() const {
+		DEV_ASSERT(tls_data.count);
+		if (--tls_data.count == 0) {
+			tls_data.lock.unlock();
+		}
+	}
+
+	_ALWAYS_INLINE_ THREADING_NAMESPACE::unique_lock<THREADING_NAMESPACE::mutex> &_get_lock() const {
+		return const_cast<THREADING_NAMESPACE::unique_lock<THREADING_NAMESPACE::mutex> &>(tls_data.lock);
+	}
+
+	_ALWAYS_INLINE_ SafeBinaryMutex() {
+	}
+
+	_ALWAYS_INLINE_ ~SafeBinaryMutex() {
+		DEV_ASSERT(!tls_data.count);
+	}
+};
+
+template <int Tag>
+class MutexLock<SafeBinaryMutex<Tag>> {
+	friend class ConditionVariable;
+
+	const SafeBinaryMutex<Tag> &mutex;
+
+public:
+	explicit MutexLock(const SafeBinaryMutex<Tag> &p_mutex) :
+			mutex(p_mutex) {
+		mutex.lock();
+	}
+
+	~MutexLock() {
+		mutex.unlock();
+	}
+
+	_ALWAYS_INLINE_ void temp_relock() const {
+		mutex.lock();
+	}
+
+	_ALWAYS_INLINE_ void temp_unlock() const {
+		mutex.unlock();
+	}
+
+	// TODO: Implement a `try_temp_relock` if needed (will also need a dummy method below).
+};
+
+GODOT_CLANG_WARNING_POP
+
+#else // No threads.
+
+template <int Tag>
+class SafeBinaryMutex {
+	struct TLSData {
+		TLSData(SafeBinaryMutex<Tag> &p_mutex) {}
+	};
+	static thread_local TLSData tls_data;
+
+public:
+	void lock() const {}
+	void unlock() const {}
+};
+
+template <int Tag>
+class MutexLock<SafeBinaryMutex<Tag>> {
+public:
+	MutexLock(const SafeBinaryMutex<Tag> &p_mutex) {}
+	~MutexLock() {}
+
+	void temp_relock() const {}
+	void temp_unlock() const {}
+};
+
+#endif // THREADS_ENABLED